Laser thermal response of a finite slab as a function of the laser pulse parameters.

Abstract

This paper deals with the problem of heating a finite slab using laser radiation in relation to the parameters characterizing the laser pulse, namely: qmax(W/m2), the maximum laser power density, t0 the time interval required to reach qmax and td, the pulse time duration. The pulse shape q t is suggested in the form: q t bqmax t=td 1 t=td exp B t t0=td , where b and B are parameters. Fitting with published experimental pulse [Ready JF. Effects due to absorption of laser radiation. J Appl Phys 1965;36:462–68] is made. Fourier series expansion technique is considered to solve the problem. The critical time required to initiate melting tm is estimated for four metallic elements and five semiconductors, namely: Al, Cu, Ag, Au (aluminum, copper, silver, and gold), cadmium sulfide, germanium, silicon, alpha beryllium oxide, and silicon carbide. Five pulses with different characteristic parameters are considered. Computations revealed that the thermal response of the targets is highly affected by qmax and to, while the pulse time duration is less effective in determining the value of tm. Moreover, it is revealed that the relation between tm and the melting temperature for the same laser pulse is nonlinear for the considered targets under the indicated conditions.